In motor vehicles having automatic transmissions and air conditioning systems, engagement of the air conditioner compressor clutch when the transmission converter clutch is engaged or on (CC-ON) has resulted in an objectionable disturbance. One solution to this problem involves a specific sequence of steps in the engine and transmission control to engage the compressor clutch. First, the engine controller sends a message to the transmission controller that the air conditioner compressor clutch is to be engaged. The transmission controller then starts electronic modulation (EMCC) of the transmission converter clutch. When slip occurs, i.e., engine and turbine speed are separated, the transmission controller sends a message to the engine controller. The engine controller then engages the air conditioner compressor clutch.
The problem with the above is that if the automatic transmission fluid has deteriorated sufficiently, there is a risk that acceptable EMCC cannot be established due to an induced system shudder. When automatic transmission fluid deteriorates (friction coefficient characteristics change), the transmission system is no longer capable of keeping EMCC operation under control when slip starts and a large disturbance or shudder typically occurs when slip starts.
It is an object of this invention to avoid the foregoing problem by determining that the automatic transmission fluid has deteriorated and when it has, bypassing the EMCC portion of the air conditioner compressor clutch engagement sequence.
It is another object of this invention to determine that the automatic transmission fluid has deteriorated by detecting shudder during the EMCC portion of the air conditioner compressor clutch engagement sequence.